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Flywheel resistance training calls for greater eccentric muscle activation than weight training
Karolinska Institutet.ORCID iD: 0000-0003-3470-5175
2010 (English)In: European Journal of Applied Physiology, ISSN 1439-6319, E-ISSN 1439-6327, Vol. 110, no 5, p. 997-1005Article in journal (Refereed) Published
Abstract [en]

Changes in muscle activation and performance were studied in healthy men in response to 5 weeks of resistance training with or without "eccentric overload". Subjects, assigned to either weight stack (grp WS; n = 8) or iso-inertial "eccentric overload" flywheel (grp FW; n = 9) knee extensor resistance training, completed 12 sessions of four sets of seven concentric-eccentric actions. Pre- and post-measurements comprised maximal voluntary contraction (MVC), rate of force development (RFD) and training mode-specific force. Root mean square electromyographic (EMG(RMS)) activity of mm. vastus lateralis and medialis was assessed during MVC and used to normalize EMG(RMS) for training mode-specific concentric (EMG(CON)) and eccentric (EMG(ECC)) actions at 90°, 120° and 150° knee joint angles. Grp FW showed greater (p < 0.05) overall normalized angle-specific EMG(ECC) of vastii muscles compared with grp WS. Grp FW showed near maximal normalized EMG(CON) both pre- and post-training. EMG(CON) for Grp WS was near maximal only post-training. While RFD was unchanged following training (p > 0.05), MVC and training-specific strength increased (p < 0.05) in both groups. We believe the higher EMG(ECC) activity noted with FW exercise compared to standard weight lifting could be attributed to its unique iso-inertial loading features. Hence, the resulting greater mechanical stress may explain the robust muscle hypertrophy reported earlier in response to flywheel resistance training.

Place, publisher, year, edition, pages
2010. Vol. 110, no 5, p. 997-1005
Keywords [en]
Concentric and eccentric actions, Electromyography, Iso-inertia, Resistance exercise
National Category
Physiology
Identifiers
URN: urn:nbn:se:kth:diva-45791DOI: 10.1007/s00421-010-1575-7ISI: 000284463900014PubMedID: 20676897OAI: oai:DiVA.org:kth-45791DiVA, id: diva2:452919
Note
QC 20111102Available from: 2011-10-31 Created: 2011-10-31 Last updated: 2018-01-12Bibliographically approved
In thesis
1. Acute and early chronic responses to resistance exercise using flywheel or weights
Open this publication in new window or tab >>Acute and early chronic responses to resistance exercise using flywheel or weights
2010 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Resistance exercise using weights typically offers constant external load during coupled shortening (concentric) and lengthening (eccentric) muscle actions in sets of consecutive repetitions until failure. However, the constant external load and the inherent capability of skeletal muscle to produce greater force in the eccentric compared with the concentric action, would infer that most actions are executed with incomplete motor unit involvement. In contrast, use of the inertia of flywheels to generate resistance allows for maximal voluntary force to be produced throughout the concentric action, and for brief episodes of greater eccentric than concentric loading, i.e. “eccentric overload”. Thus, it was hypothesized that acute flywheel resistance exercise would induce greater motor unit and muscle use, and subsequent fatigue, compared with traditional weight stack/free weight resistance exercise. Furthermore, it was hypothesized that flywheel training would induce more robust neuromuscular adaptations compared with training using weights.

A total of 43 trained and untrained men were investigated in these studies. Knee extensor muscle activation, fatigue response and muscle use were assessed during exercises by recording electromyographic signals and by means of functional magnetic resonance imaging, respectively. Flywheel resistance exercise provoked maximal or near maximal muscle activation from the first repetition, induced robust fatigue, and prompted more substantial motor unit and muscle use than weight stack/free weight resistance exercise in both novice and resistance trained men. Both prior to and following five weeks of unilateral knee extension training, the eccentric muscle activation was greater with flywheel than weight stack training. Furthermore, weight stack training generated greater increases of dynamic strength and neural adaptations, while flywheel training generated more prominent hypertrophy of individual quadriceps muscles and greater improvement of maximal isometric strength.

Hence, due to the preferential metabolic cost of the concentric rather than eccentric actions, the maximal activation through the entire range of the concentric action within each repetition of a set during flywheel resistance exercise probably evoked the marked fatigue, and prompted more substantial muscle use than resistance exercise using weights. Furthermore, while any cause-effect relationship remains to be determined, results of the present study suggest that brief episodes of “eccentric overload” amplify muscular adaptations following concentric-eccentric resistance training.

Place, publisher, year, edition, pages
Östersund: Mittuniversitetet, 2010. p. 50
Keywords
electromyography, flywheel, magnetic resonance imaging, resistance exercise
National Category
Physiology
Identifiers
urn:nbn:se:kth:diva-48477 (URN)
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Supervisors
Note
QC 20111206Available from: 2011-12-07 Created: 2011-11-18 Last updated: 2018-01-12Bibliographically approved

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